What are the main factors affecting the extraction time of Espresso in espresso extraction?

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Three main factors affecting the extraction time of Espresso: grinding degree, pump pressure and water output, powder bowl

[degree of grinding]

Imagine two water pipes, one full of stone and the other full of sand. Now imagine pumping water into these two pipes. Obviously, the water will be better able to pass through the one full of stones.

The effect of grinding degree on Espresso extraction is similar. The finer the grinding, the slower the flow rate. The thicker the grinding, the faster the flow rate. Almost every bean grinder can adjust the grinding degree, giving you the freedom to adjust the extraction time under a fixed liquid weight.

[pump pressure and water output]

The pump pressure of most Italian machines is set at about 9 Pa. This pressure can satisfy most application scenarios, although there are many experiments on different constant pressure and variable pressure extraction-this part is too advanced to be discussed today. You only need to know that the lower the extraction pressure is, the slower the extraction flow rate of Espresso is, and the amount of water produced by the machine will be reduced.

[powder bowl]

The size and quantity of the pore diameter of the powder bowl will affect the extraction rate of Espresso. This is called the "total open area" or TOA (total open area). The larger the TOA, the easier it is for water to flow through the powder bowl.

[back to grinding]

Once your powder quantity and liquid weight are determined, adjusting the extraction time gives you the last chance to adjust the extraction rate. Adjusting the degree of grinding is the only one that can increase or reduce the concentration and extraction rate at the same time.

Most of the time, if the grinding degree is fine, the extraction rate and concentration will increase at the same time. Fine grinding increases the contact area between coffee powder and water, thus improving the extraction rate. At the same time, finer grinding prolongs the extraction time, which will also increase the extraction rate of coffee.

[change grinding]

The adjustment of each bean grinder is a little different, but for a particular machine, you can quickly learn how to increase the extraction time by 2 seconds or reduce the extraction time by 5 seconds.

If your Espresso extraction is too fast or too slow, you need to adjust the grinding. Once you have adjusted the grinding, you must remove the coffee powder that remained in the channel of the bean grinder.

If you use a regular bean grinder, you must observe and adjust the amount of powder after grinding. While adjusting the degree of grinding, you also change the amount of coffee you grind per second. Observe the change of the amount of coffee powder grinded at any time.

Keeping an adequate amount of coffee beans in the warehouse will also help improve the stability of the grinding. If there are fewer coffee beans in the warehouse, the weight of the coffee beans on the grinding plate will be reduced. For some bean grinders, even if the grinding degree is kept constant, this situation will make the extraction speed of Espresso much faster.